This invention relates to an oscillatory wave generator which generates a plurality of waves respectively having submultiple related frequencies and is particularly suitable for tone generators in electronic musical instruments.
The tone generator of an electronic musical instrument, which employs a frequency division circuit, is well known in the art. In this tone generator, the signal having the highest frequency is subjected successively to frequency division with a plurality of frequency division circuits, thereby to obtain in parallel a plurality of square wave signals having octavely related frequencies. For instance, if it is assumed that the number of notes in one octave is twelve (12) and the number of octaves is five (5), then sixty (60) different signals are provided in parallel. These signals, namely, tone source signals are selectively utilized in response to key depression in a keyboard. In the case where a plurality of tone production channels are provided to make it possible to simultaneously produce a plurality of tones, all of the signals are supplied to each of the tone production channels, so that in each tone production channel, the signals of tones assigned thereto are selected. In this case, as all of the signals are supplied to each of the tone production channels as described above, it is necessary to provide a large number of signal supplying lines. This is one of the disadvantages accompanying the conventional tone generator described above. For instance, if the number of channels is twelve (12), then 720 (=60.times.12) signal supplying lines are required. Reduction of the lines may be accomplished by employing a method in which frequency division circuits are provided for each channel, and the signal having the highest frequency out of the frequencies of the notes (C-B) is applied to each frequency division circuit. However, this method is still disadvantageous in that, since the frequency divisions are effected individually in the channels, when tones having the same note are assigned to different channels, their phases may sometimes be opposite to each other. For instance, in the case where tones having the same note are assigned to two channels, if the phases of the frequency division outputs of the two channels are opposite to each other, the tones produced by the two channels cancel each other; that is, no tone is produced at all.